Geography Unit 1

Geography Unit 1

1. Volcanic Activity

   • Lava: Liquid rock (above ground)
   • Magma: Liquid rock (below ground)
   • Ash & Cinder: Small Molten fragments
   • Vent: Single opening through which volcanic activity erupts
   • Mild Eruptions: Thin Lava flows, Little to no ash and cinders, Small amounts of gas
   • Explosive Eruptions: Thick lava flows, Ash and cinders
   • Types of Volcanos:
     • Ash & Cinder Cone: -Explosive eruptions with ash and cinders. -Symmetrical shape -Thick rapidly solidifying lava -Steep sides -Large crater
     • Composite Cone: -Periods of quiet and explosive activity. -Layers of ash and cinder intermixed with layers of lava. -Weak spots may develop forming small craters.
     • Shield Cone: -Thin liquid lavas. -Milder eruption. -Broad flat cone. -Little to no ash and cinders.
   • How Volcanos Erupt: Along plate boundaries heat is generated due to friction, intense heat melts rock beneath crust producing magma, if reaches surface through fractures or vents extrusive volcanic activity takes place.

2. Forces/ Plate Movements

   • Tensional force: Stretching force in the earths crust.
     • May form trenches or ridge zones
       • Ridge Zone: Occurs where two plates move apart. Magma may rise between the plates and form a ridge.
     • Caused when: Plates break apart and move away from or post eachother.
       • A normal fault is when a plate on side drops down lower than the plate on the other side. This occurs when tensional forces exist
   • Compressional force: A force pushing into a part of the earths crust causing it to buckle.
     • Caused when two plates move towards each other and squeeze together which causes rock to bend, or be pushed upwards
       • Reverse faults are caused when plates are pushed together. One rock is pushed up over the other.
     • May form subduction zones
     • When two plates move towards each other they create compressional forces. As a result folding occurs. Folding is the process whereby layers of rock bend and are pushed upward forming mountains.
       • Anticline: An arch like up fold in bended, contorted rock
       • Syncline: An arch like down fold in bended contorted rock.

3. Denudation

   • Denudation: Refers to the wearing down or smooting off of land features.
   • Weathering: The breakdown of rock and minerals.
     • Physical weathering: breakdown of rock and minerals by mechanical stress
       • Frost fracture: The expansion of freezing water that causes rocks to crack.
       • Heat expansion: Rocks can expand and subsequently fracture.
       • Exfoliation: As internal pressure is released from certain rocks, it can cause layers to split and fall off.
       • Plant growth: Expansion due to root.
       • Burrowing animals: Tunneling animals can increase the size of existing cracks.
       • Environments effect on physical weathering
         • Fast temperature changes increases the amount of physical weathering due to to heat expansion
         • Abundant precipitation combined with alternating freezing/ thawing temperatures increases the amount of frost fracture
         • Running water increases physical erosion as friction occurs between water and rocks.
     • Chemical weathering: breaks down rock with chemical reactions often including water.
       • Solutions- As rain water absorbs chemicals from the atmosphere it then reacts with rock and minerals causing some to dissolve and move away
       • Hydrolysis- Carbonic acid reacts with silicates in some rocks leaving a soft clay from which sodium magnesium and potassium are subsequently leached.
       • Oxidation- Reaction of metallic minerals to oxygen (mainly in water) Results in formation of oxides. Ex. Rust
       • Environments affect on chemical weathering
         • Heavy rain- running water and abundance of water increases the amount of dissolving that occurs.
         • High temperature- will increase the rate of chemical reactions like oxidation.
         • Ocean water- contains salt which can increase the rate of many reactions like oxidation.
   • Erosion: A two-fold process that starts with breakdown of land (weathering) and also includes the movement (transportation) of these weathered materials. And then the deposition of the eroded material occurs when it is dropped in a new location.

4. Life Cycle of a River

   • Youth
     • Usually found in high land or mountain regions
     • Steep slope
     • Small volume of water
     • Rapid flow of water
     • Rapid vertical erosion
       • Vertical erosion- makes rivers deeper
     • Narrow v-shaped valley
     • Waterfalls and rapids are common
   • Maturity
     • High relief is eroded
     • Gentler slope
     • Well-developed tributaries
     • Broad flat river valley
     • Lateral erosion
       • Horizontal erosion- makes rivers wider
     • Meandering results
   • Old age
     • No slope
     • Little relief
     • Elaborate meandering
     • Oxbow lakes
     • Swampy areas
     • Very muddy due to slow speed
     • Susceptible to flooding due to large flood plain

5. Deltas

   • A low-lying area at themouth of a river formed by deposition of silt
     • Arcuate delta- fan shaped
     • Digitate delta- delta with long fingers of sediment reaching into the sea.
     • Estuarine delta- delta that runs into a bay or estuary

6. Glaciers

   • Continental Glacier: A mass of ice situated over most of a continent which may be moving, or has moved, overland.
     • Outwash Plain: Like a river delta, melt water flowing, from glacier deposits silt like river deltas. Silt is deposited in layers. Small particles are carried further away. Larger particles drop closer to the glacier.
     • Terminal moraine: Heap of ridge of bulldozed gravel that marks the end of the forward motion of a glacier. As a glacier retreats it deposits debris/gravel
     • Erratic's: Large boulders that look very out of place.
     • Drumlins: Egg shaped hill. Formed under glaciers. Pointy end points in direction of ice flow.
       • Formation: Ice melts under glacier, deposits of gravel are made, glacier moves forward, deposits are bull-dozed along and catches up in rough areas forming piles or drumlins.
     • Eskers: Long deposits of eroded glacial material. Formed by sub-glacial streams that deposits material like all rivers. "highways of the north"
   • Alpine Glacier: Are like very slow moving rivers of ice flowing down high mountain valleys
     • Only found on mountain tops
     • Smaller than continental glaciers
     • Cirque: A circular hollow cut into bedrock during glaciation. Side and back walls are steep but front walls open downward.
       • Arete: Steep knife edged ridge between two cirques in a mountain region.
       • Formation: Alpine glaciers freeze onto mountain valley and as it proceeds it chips away at rock on the mountain top leaving a cirque shape.
     • Hanging valley- A high level tributary valley from which ground falls sharply to the level of the lower, main valley.
     • Lateral moraine: a landform deposited by a glacier or ice sheet on the side of a glacier
     • Terminal moraine: Deposits that mark the farthest extent of the alpine glacier (same with continental glaciers)
     • Fjords: When alpine glaciers erode through valleys in the mountain. Glacier valley reaches the coast. Glacier melts and sea water flood of the valley.
   • Both move and cause erosion, both change the landscape, both develop in constantly cold temperatures below freezing
     • Direction of glacial movement: Gently sloped end of drumlins point in the direction of glacier movement. Terminal moraine marks the furthest extent of the glacier. Layers of silt in an outwash plain can indicate the glacier movement, fine particles would be at the leading edge while large particles would have been closer to the glacier.